1. Field of the Invention
The present invention relates to a dehumidifier. More particularly, it pertains to an apparatus which dehumidifies gas, such as air or the like, by refrigerating it.
2. Description of the Related Art
Industrial-purpose air cylinders, which have extendable piston rods, are used for movement of mechanical devices. High precision in extension and retraction of the piston rods is required in, for instance, production system lines especially where sequential movement of related parts is involved. Therefore, prevention of rust in pressure chambers, which accommodate the piston rods, of the air cylinders is extremely important for smooth movement of the piston rods. Accordingly, it is necessary that dehumidified air be supplied to the pressure chambers of the air cylinders. Also, air must be dehumidified for hygiene purposes when, for instance, released into a patient's mouth during dental treatment. Air used in these fields are normally dehumidified by refrigerating type dehumidifiers.
A typical refrigerating type dehumidifier is generally provided with a refrigerating circuit which includes a compressor, a condenser, etc. A refrigerant is cooled in this circuit to cool air and thus dehumidify it.
More specifically, referring to FIG. 7, a typical dehumidifier 71 has a housing 74 which houses a precooling/reheating chamber 72, a cooling chamber 73, and a refrigerating circuit R for cooling of the chamber 73. A compressor 75 is connected to the refrigerating circuit R to compress refrigerant gas inside the circuit R. A condenser 76 is provided in the circuit R downstream of the compressor 75. A fan 78, connected to a motor 77, is located in the vicinity of the condenser 76. When the motor 77 rotates the fan 78, an air current is produced. This directs the air inside the housing 74 toward the condenser 76 and cools the compressed refrigerant gas supplied to the condenser 76 from the compressor 75.
A capillary tube 79 is disposed downstream of the condenser 76. The pressure of the liquefied refrigerant is lowered when it flows through the tube 79. A zigzagged refrigerating passageway 80 is provided downstream of the tube 79 inside the cooling chamber 73. Refrigerant flowing through the passageway 80 is vaporized when it cools the interior of the cooling chamber 73. The vaporized refrigerant, or refrigerant gas, is then conveyed to the compressor 75.
A cooling passage 81 defined inside the cooling chamber 73 is connected to an air supply pipe 83 by a zigzagged precooling pipe 82 provided in the precooling/reheating chamber 72. An air compressor 84, which supplies relatively hot and humid air, is connected to the supply pipe 83. A connecting pipe 85 joins the cooling passage 81 to a reheating pipe 86. The reheating pipe 86, formed in a zigzagged manner, is arranged to contact the precooling pipe 82. An air discharge pipe 87 is connected to the downstream side of the reheating pipe 86.
When the air compressor 84 is actuated, air is delivered to the cooling passage 81 via supply pipe 83 and precooling pipe 82. Heat is transferred from the delivered air to the refrigerant flowing through the refrigerating passageway 80. Subsequent to the cooling and dehumidification, the dehumidified air is sent to external devices such as air cylinders or the like via the connecting pipe 85, reheating pipe 86, and air discharge pipe 87.
Water separated from the air delivered into the cooling chamber 73 is discharged from a drain outlet 88 provided in the chamber 73. The drain outlet 88 communicates with a draining device 89 and a draining pipe 90. Water entering the drain outlet 88 is discharged into a drainage ditch 91, shown in FIG. 9, by way of the draining device 89 and the draining pipe 90.
The prior art dehumidifier 71 requires the draining pipe 90 and the drainage ditch 91 to discharge water with the draining device 89. Therefore, it is necessary to couple the draining pipe 90 to the dehumidifier 71 and to prepare a drainage ditch 91.
Furthermore, in locations where a drainage ditch 91 is not prepared, the draining pipe 90 may be connected to a drainage container 92 such as the one shown in FIG. 8 to collect water discharged by the draining device 92. However, the water which collects in the container 92 must be disposed of periodically or the container 92 itself must be exchanged with a new one when it becomes full. This results in burdensome work such as carrying the container 92 and connecting the container 92 with the draining pipe 90.
In addition, cooling by the refrigerant causes water in the ambient air to condense on the outer walls of the cooling chamber 73 and on the outer surface of the refrigerating circuit R at the sections leading into and out of the chamber 73, which are at the upstream and downstream sides of the refrigerating passageway 80. Dewdrops fall to the bottom of the housing 74 and stain the inside of the housing 74. Accordingly, it has been necessary to wrap the refrigerating circuit R with a heat insulating material to prevent heat exchange between the housing 74 and the ambient air and also between the refrigerating circuit R at the upstream and downstream sides of the refrigerating passageway 80 and the ambient air.